This invention relates to forage harvesters and more particularly to a feed roll drive mechanism therefor wherein a hydrostatic transmission is utilized to vary the length of cut of crops processed by the chopping mechanism.
The ability to vary the length of cut of crops processed by the forage harvester is a necessary feature thereof, since various factors, such as type of silo and type of animal, for example, beef cattle or dairy cattle, are said to require longer or shorter cuts of silage for the most efficient utilization thereof.
Heretofore forage harvesters have had a mechanical drive for driving the feed roll mechanism. In order to vary the length of cut, various gear combinations were provided to change the speed of the feed rolls relative to the chopper. On some machines, a gear had to be physically changed to achieve this result. Others have provided mechanical shifters for switching from one gear to another. A further means of changing the length of cut involved removing a number of blades from the chopper. However, all of these arrangements suffer the common disadvantage of having the length of cut restricted to a few optional choices, some of which require interchanging or removing parts.